1. Field of the Invention
The present invention relates generally to devices that are used to apply heat to shrink wrap material, and more particularly is a hot air lamination chamber for medical catheters.
2. Description of the Prior Art
The manufacture of a medical catheter involves multiple processes and the utilization of sometimes very expensive materials. The basic procedure includes wrapping a central tubular element with conductive and/or sensing wires, then covering the wires with a protective outer sleeve. Because of the nature of operations involving catheters, the outer sleeve must be a smooth, low friction surface. While some catheters can be manufactured using an extrusion process to provide the outer sleeve, many of the wire wrappings used on the catheters are too delicate for such operations. The outer sleeve in these cases is typically shrink tubing, and is applied using heat to shrink the sleeve onto the wires and central tube of the catheter in a lamination process.
The heat shrink lamination operation can occur at very high temperatures −650° F. or higher. The operating temperature must be held steady at the desired temperature or negative results occur. For example, a shrink tube that shrinks at 650° F. may well melt if the temperature reaches 670° F. Therefore the temperature of the environment in which the heat shrink or lamination operation is performed must be maintained at a steady state.
Current art processes utilize either a radiant electric heater or a total-loss compressed air heating system. Systems using a radiant electric heater have a very difficult time controlling the temperature of the product. While the calibration thermocouple used in the device can be held at the proper temperature, the temperature of the product being processed can undergo a temperature fluctuation of up to ±50° F. Such temperature fluctuations can easily ruin the lamination process, thereby requiring scrapping of the part. As indicated above, the part at that point has already had significant manufacturing process hours invested, and may embody some very expensive materials.
The other type of current art device, the total loss compressed air heating systems, have much better temperature control. However, the hot air used to laminate the product is exhausted to the room in which the process takes place. This can be very undesirable, as the processing is most often in an air conditioned clean room. In addition to the exhausted air, compressed air heating systems require pneumatic plumbing. Equipment with pneumatic plumbing is more difficult to maintain in conformance to US National Fire Protection Association standards (e.g. NFPA-79) and European CE standards. The pneumatic systems have to be separated from the rest of the electronics to prevent problems such as line moisture causing electrical shorts.
Accordingly, it is an object of the present invention to provide a lamination chamber that can maintain a very steady elevated temperature.
It is another object of the present invention to provide a method of constructing a catheter that increases the yield of a lamination process.
It is a still further object of the present invention to provide a process that does not exhaust a large amount of hot air into an air conditioned clean room environment.
It is yet another object of the present invention to provide a device that does not require pneumatic plumbing.